The present invention relates to a grommet for tightly sealing the clearance between a panel of a vehicle or the like and an electric cord inserted through a hole of the panel.
FIG. 1 shows a longitudinal sectional view of a grommet, disclosed in U.S. Pat. Ser. No. 217,029 filed on July 11, 1988 , now U.S. Pat. No. 4,839,937, which tightly seals the clearance between a panel of a vehicle or the like and an electric cord inserted through a hole of the panel and supports the cord so that the cord is protected from damage. The grommet has a soft portion A including a base 1 shaped as a hollow disk and a cylindrical tube 2 provided at the inner circumferential edge of the base so that the electric cord W, which extends through the hole of the panel P and is supported by the grommet is inserted into the tube. A tape 3 is wound on the electric cord W and the tube 2 so that the cord and the tube are securely sealed to each other. A cylindrical peripheral wall 4 is provided at the outer circumferential edge of the base 1 opposite the tube 2. An annular support part 5 extends inward from the bottom of the peripheral wall 4 so that an annular recess 6 is defined inside the peripheral wall. Lips 7 and 8, which are located in contact with the panel P, are provided on the outside surface of the support part 5. The grommet also has a locking portion B made of hard resin and including a lower part 9 having a center hole, an upper annular wall 10 extending along the peripheral edge of the lower part, and a base plate 11 provided at the top of the annular wall and having a center hole. The annular wall 10 is partially cut and bent outwardly so that a plurality of engaging tongues 12 are formed.
The engaging tongues 12 have engaging steps 12a at the outside surfaces of the tips of the tongues. The tongues 12 are flexible such that the engaging steps 12a are engaged in the hole of the panel P as the tongues are elastically bent inward. The annular recess 6 of the soft portion A of the grommet is fitted with the base plate 11 of the locking portion B engaged in the hole of the panel P, so that the lips 7 and 8 are tightly fitted on the panel to seal it. As a result, the panel P and the electric cord W are sealed to each other so that rain water or the like cannot enter through the hole of the panel. Besides, the cord W is supported by the tube 2 so that the cord is protected from damage. However, when an external force F acts on the electric cord W, the cord and the tube 2 are displaced together in the direction of the force and the base 1 and the peripheral wall 4 are pulled in the direction of the force so that the base and the wall are displaced and deformed. Simultaneously, the lips 7 and 8 may separate from the panel P so that the sealing of the panel deteriorates. This presents a problem. If the base 1 and the peripheral wall 4 are pulled further in the direction of the force F, the annular recess 6 might dislodge from the base plate 11. This also presents a problem.
In order to solve these problems, one or a plurality of flat cord fastening parts 13 are provided to extend from the inner circumferential edge of the lower wall 9, and a tape 14 is wound on the fastening parts and the electric cord W. As a result, the locking portion B engaged in the panel P prevents the cord W from being displaced in the direction of the external force F and separating the soft portion A from the locking portion, because the external force acts on the cord to pull the soft portion and the locking portion together in the direction of the force. The problems are thus solved.
FIG. 2 shows a longitudinally sectional view of another grommet, also disclosed in the above-mentioned patent, which also tightly seals the clearance between a panel of a vehicle or the like and an electric cord inserted through a hole of the panel and supports the cord so that the cord is protected from damage. The grommet comprises a soft portion A and a locking portion B made of a hard resin and including a base plate 11 and an electric cord fastening part 16 coupled to the inner circumferential edge of the base plate by a flexible thin bendable part 15. The stopper 16a of the cord fastening part 16 is located near the outside surface of the lower part 9 of the locking portion B. A tape 14 is wound on the cord securing part 16 and the electric cord W. When an external force F acts on the cord W, the cord is moved in the direction of the force so that the stopper 16a comes into contact with the lower part 9 to prevent the cord from being moved further in the direction. Thus, movement of the cord W is minimized. The small extent of movement is absorbed by the small deformation of the curved joint of the base 1 and tube 2 of the soft portion A so that the lips 7 and 8 of the soft portion are prevented from separating from the panel P and the soft portion is prevented from separating from the locking portion B.
Although the electric cord fastening parts 13 of the conventional grommet shown in FIG. 1 have enough resistance to an external force G whose direction is inverse to that of the other external force F, the fastening parts are buckled, as shown in FIG. 3, if the external force F pulling the electric cord W is strong, so that the cord is moved in the direction of the force to separate the lips 7 and 8 from the panel P and possibly separate the soft portion A from the locking portion B. This is a problem.
Referring to FIG. 2, even if the external force F is strong the stoppers 16a of the halfway sections of the electric cord fastening parts 16 of the conventional grommet are supported by the lower part 9. Therefore, a compressive load only acts on the cord fastening parts under the stoppers so that it is less likely that the fastening parts will buckle. However, when an external force G, whose direction is inverse to that of the other external force F, acts on the electric cord W, as shown in FIG. 4, the thin bendable part 15 is likely to be severed. This is also a problem.